A second set of playlists selecting by genre and mood rather than by play
history: eighties synths, high energy rock, screamo, drum and bass, dance,
classic rock.
The tags come from Last.fm rather than MusicBrainz. MusicBrainz genres arrive
free with the Lidarr index, which makes them the obvious choice and the wrong
one: they are sparse and formal, and will not tell you a record is screamo or
synthwave. Crowd tags will, because people typed them.
One request per artist, by MusicBrainz id where Lidarr has one, refreshed every
ninety days. An artist Last.fm has never heard of is recorded as fetched with no
tags rather than left unmarked, so it is not asked about again on every pass
forever. The tag table is keyed on the normalised artist name, not the Lidarr
id, so it survives an artist being removed and re-added there.
Weights are taken from the response's count where it has one. The documented
sample carries only a name and a URL, a live response also carries a 0-100
count, and depending on either alone would be a guess -- so the count is used
when present and the documented ordering by popularity stands in when it is not.
An artist qualifies for a mood when their weights inside it sum to at least
thirty. A single low-weight tag is not a genre, it is somebody's stray opinion.
A mood may also restrict release years, which is what separates eighties synth
records from everything else a synthpop tag drags in.
The built-in set is chosen for this library rather than as a taxonomy, and
--vibes replaces it wholesale with a JSON file so a new mood does not need a new
release. Names are validated when that file is read: an invalid one would
otherwise only surface as a playlist written somewhere unintended.
Emma Thorpe